This invention relates generally to the field of microstructures, and more particularly to detecting and measuring position or deflection changes of a microstructure in a microsensor.
Microsensors are being utilized more frequently as the desire to reduce the size of mechanical systems increases. Microsensors are becoming important detectors for military, industrial and consumer applications such as atomic force microscopy, chemical sensing, pressure or flow sensing, infrared detection, diaphragms, military safing and arming systems, and for use in accelerometers. In some cases, an array of microsensors is employed in applications such as infrared detection or chemical sensing.
A variety of microstructures can be used in a microsensor to detect and measure changes. For example, a microstructure such as a microcantilever can be used as a detector to produce a small deflection in the presence of a changing condition, whether that is the presence of a chemical or a particular type of radiation, or even changing temperature. Other types of microstructures can be used in microsensors for varying purposes, depending upon the property or characteristic to be measured.
A problem in using a microstructure such as a microcantilever as a detector is the measurement of small deflections of the microstructure. Capacitance methods, piezoresistance devices, and tunneling sensors are often used to measure small deflections of a microcantilever. For example, this can be accomplished by coupling an electrical circuit into the microcantilever which can be used to measure changes in resistance or capacitance with deflection.
However, the use of conventional systems and methods introduces unwanted influences or noise upon the microstructure in the microsensor, especially when multiple microcantilevers are used. For example, capacitance methods induce noise such as electrostatic forces onto the microcantilever being used in the microsensor. In another example, piezoresistance devices induce noise such as resistive heating onto the microcantilever being used in the microsensor.
Unwanted influences on the microstructure also affect the range and sensitivity of the microsensor. The deflection response of a microcantilever is dependent upon the width and thickness of the microcantilever beam. For example, a relatively thin microcantilever beam could be affected by electrostatic forces or resistive heating introduced by conventional systems and methods. In another example, piezoelectric methods lack the precise positioning resolution.
Laser measurement methods as used with conventional atomic force microscopes offer accurate methods of measuring small deflections of microcantilevers. However, these methods are difficult to transfer to a system requiring an array of microcantilevers. When these methods are used with an array of microcantilevers, the bulk and size of the lasers offset any reduction in size gained by the use of microcantilevers.
Microstructures can be constructed with a layer thickness of 2 xcexcm or less. The alignment of these relatively thin microstructures in a microsensor can be difficult and time consuming. Therefore, the costs to fabricate microsensors with thin microstructures can be very expensive.
Thus, there is a need in the art for an improved apparatus and method for detecting a change in the position or deflection of a microstructure in a microsensor.
There is yet a further need in the art for an apparatus and method that minimizes unwanted influences in detecting and measuring changes in the position or deflection of a microstructure in a microsensor.
There is yet a further need in the art for an apparatus and method that increases the range and sensitivity of detecting and measuring changes in the position or deflection of a microstructure in a microsensor.
There is yet a further need in the art for an apparatus and method that decreases the cost of fabricating and aligning thin microstructures for microsensors.
The present invention meets the needs described above in an integrated optical sensing element. The integrated optical sensing element provides an improved apparatus and method for detecting a change in the position or deflection of a microstructure in a microsensor. The integrated optical sensing element minimizes unwanted influences in detecting and measuring changes in the position or deflection of a microstructure in a microsensor. Furthermore, the integrated optical sensing element increases the range and sensitivity of detecting and measuring changes in the position or deflection of a microstructure in a microsensor. And, the integrated optical sensing element decreases the cost of fabricating and aligning thin microstructures for microsensors.
Generally described, the invention is an integrated optical sensing element for detecting changes in position or deflection. The integrated optical sensing element includes a deflectable member, a waveguide, and a means for measuring the extent of position change or deflection of the deflectable member by receiving a light beam from the deflectable member. The deflectable member is configured to receive the light beam. The waveguide is configured to redirect the light beam in response to a change in position or deflection of the deflectable member. The means for measuring the extent of position change or deflection of the deflectable member receives the light beam from the deflectable member. Changes in the light beam are then correlated to changes in the position or deflection of the deflectable member.
According to an aspect of the invention, an integrated optical sensing element can be configured with a waveguide disposed to reflect the light beam. An integrated optical sensing element can be configured with a waveguide or optical waveguide adjacent to the deflectable member. When the light beam travels along the waveguide, the waveguide can reflect the light beam towards the deflectable member, and then the light beam can be reflected back towards the waveguide, optical waveguide, or a means for measuring the extent of position changed or deflection of the deflectable member.
If the light beam is reflected towards the means for measuring the extent of position change or deflection of the deflectable member, then the means can be photodetector or other sensing device that measures the relative power or intensity of the reflected light beam. The measured changes in relative power or intensity of the reflected light beam can be correlated to changes in the position or deflection of the deflectable member.
If the light beam is transmitted back through the waveguide or optical waveguide, then the means for measuring the extent of position changed or deflection of the deflectable member receives the reflected light beam. The means can be an interferometer, or other detecting device that measures the relative distance or displacement of the reflected light beam. The measured changes in relative distance or displacement of the reflected light beam can be correlated to changes in the position or deflection of the deflectable member.
According to yet another aspect of the invention, the waveguide is operatively associated with the deflectable member so as to deflect when the deflectable member deflects. An integrated optical sensing element can be configured as a compact, modular, monolithic microstructure with a waveguide or optical waveguide embedded in the deflectable member. The waveguide or optical waveguide can be configured to direct the light beam onto a means for detecting changes in the position or power of the light beam. The measured changes in the position or power of the light beam can be correlated to changes in the position of the deflectable member to calculate the deflection or change in position of the microstructure. Means for detecting changes in the power of the reflected light beam can be a photodetector, or other detecting device that measures the relative power or intensity of the reflected light beam.
In yet another aspect of the invention, an array of integrated optical sensing elements can be arranged to provide two-dimensional imaging. A single light source can generate an incident light beam along an integrated optical circuit, where the light beam splits into attenuated light beams supplying each integrated optical sensing element. The attenauted light beams can then be used to measure or detect the change in position or deflection of a deflectable member in each integrated optical sensing element.
That the invention improves over the drawbacks of the prior art and accomplishes the advantages described above will become apparent from the following detailed description of the exemplary embodiments and the appended drawings and claims.